diff options
Diffstat (limited to 'fs/timerfd.c')
| -rw-r--r-- | fs/timerfd.c | 227 |
1 files changed, 227 insertions, 0 deletions
diff --git a/fs/timerfd.c b/fs/timerfd.c new file mode 100644 index 000000000000..e329e37f15a8 --- /dev/null +++ b/fs/timerfd.c @@ -0,0 +1,227 @@ +/* + * fs/timerfd.c + * + * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> + * + * + * Thanks to Thomas Gleixner for code reviews and useful comments. + * + */ + +#include <linux/file.h> +#include <linux/poll.h> +#include <linux/init.h> +#include <linux/fs.h> +#include <linux/sched.h> +#include <linux/kernel.h> +#include <linux/list.h> +#include <linux/spinlock.h> +#include <linux/time.h> +#include <linux/hrtimer.h> +#include <linux/anon_inodes.h> +#include <linux/timerfd.h> + +struct timerfd_ctx { + struct hrtimer tmr; + ktime_t tintv; + spinlock_t lock; + wait_queue_head_t wqh; + int expired; +}; + +/* + * This gets called when the timer event triggers. We set the "expired" + * flag, but we do not re-arm the timer (in case it's necessary, + * tintv.tv64 != 0) until the timer is read. + */ +static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr) +{ + struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx, tmr); + unsigned long flags; + + spin_lock_irqsave(&ctx->lock, flags); + ctx->expired = 1; + wake_up_locked(&ctx->wqh); + spin_unlock_irqrestore(&ctx->lock, flags); + + return HRTIMER_NORESTART; +} + +static void timerfd_setup(struct timerfd_ctx *ctx, int clockid, int flags, + const struct itimerspec *ktmr) +{ + enum hrtimer_mode htmode; + ktime_t texp; + + htmode = (flags & TFD_TIMER_ABSTIME) ? + HRTIMER_MODE_ABS: HRTIMER_MODE_REL; + + texp = timespec_to_ktime(ktmr->it_value); + ctx->expired = 0; + ctx->tintv = timespec_to_ktime(ktmr->it_interval); + hrtimer_init(&ctx->tmr, clockid, htmode); + ctx->tmr.expires = texp; + ctx->tmr.function = timerfd_tmrproc; + if (texp.tv64 != 0) + hrtimer_start(&ctx->tmr, texp, htmode); +} + +static int timerfd_release(struct inode *inode, struct file *file) +{ + struct timerfd_ctx *ctx = file->private_data; + + hrtimer_cancel(&ctx->tmr); + kfree(ctx); + return 0; +} + +static unsigned int timerfd_poll(struct file *file, poll_table *wait) +{ + struct timerfd_ctx *ctx = file->private_data; + unsigned int events = 0; + unsigned long flags; + + poll_wait(file, &ctx->wqh, wait); + + spin_lock_irqsave(&ctx->lock, flags); + if (ctx->expired) + events |= POLLIN; + spin_unlock_irqrestore(&ctx->lock, flags); + + return events; +} + +static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count, + loff_t *ppos) +{ + struct timerfd_ctx *ctx = file->private_data; + ssize_t res; + u32 ticks = 0; + DECLARE_WAITQUEUE(wait, current); + + if (count < sizeof(ticks)) + return -EINVAL; + spin_lock_irq(&ctx->lock); + res = -EAGAIN; + if (!ctx->expired && !(file->f_flags & O_NONBLOCK)) { + __add_wait_queue(&ctx->wqh, &wait); + for (res = 0;;) { + set_current_state(TASK_INTERRUPTIBLE); + if (ctx->expired) { + res = 0; + break; + } + if (signal_pending(current)) { + res = -ERESTARTSYS; + break; + } + spin_unlock_irq(&ctx->lock); + schedule(); + spin_lock_irq(&ctx->lock); + } + __remove_wait_queue(&ctx->wqh, &wait); + __set_current_state(TASK_RUNNING); + } + if (ctx->expired) { + ctx->expired = 0; + if (ctx->tintv.tv64 != 0) { + /* + * If tintv.tv64 != 0, this is a periodic timer that + * needs to be re-armed. We avoid doing it in the timer + * callback to avoid DoS attacks specifying a very + * short timer period. + */ + ticks = (u32) + hrtimer_forward(&ctx->tmr, + hrtimer_cb_get_time(&ctx->tmr), + ctx->tintv); + hrtimer_restart(&ctx->tmr); + } else + ticks = 1; + } + spin_unlock_irq(&ctx->lock); + if (ticks) + res = put_user(ticks, buf) ? -EFAULT: sizeof(ticks); + return res; +} + +static const struct file_operations timerfd_fops = { + .release = timerfd_release, + .poll = timerfd_poll, + .read = timerfd_read, +}; + +asmlinkage long sys_timerfd(int ufd, int clockid, int flags, + const struct itimerspec __user *utmr) +{ + int error; + struct timerfd_ctx *ctx; + struct file *file; + struct inode *inode; + struct itimerspec ktmr; + + if (copy_from_user(&ktmr, utmr, sizeof(ktmr))) + return -EFAULT; + + if (clockid != CLOCK_MONOTONIC && + clockid != CLOCK_REALTIME) + return -EINVAL; + if (!timespec_valid(&ktmr.it_value) || + !timespec_valid(&ktmr.it_interval)) + return -EINVAL; + + if (ufd == -1) { + ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); + if (!ctx) + return -ENOMEM; + + init_waitqueue_head(&ctx->wqh); + spin_lock_init(&ctx->lock); + + timerfd_setup(ctx, clockid, flags, &ktmr); + + /* + * When we call this, the initialization must be complete, since + * anon_inode_getfd() will install the fd. + */ + error = anon_inode_getfd(&ufd, &inode, &file, "[timerfd]", + &timerfd_fops, ctx); + if (error) + goto err_tmrcancel; + } else { + file = fget(ufd); + if (!file) + return -EBADF; + ctx = file->private_data; + if (file->f_op != &timerfd_fops) { + fput(file); + return -EINVAL; + } + /* + * We need to stop the existing timer before reprogramming + * it to the new values. + */ + for (;;) { + spin_lock_irq(&ctx->lock); + if (hrtimer_try_to_cancel(&ctx->tmr) >= 0) + break; + spin_unlock_irq(&ctx->lock); + cpu_relax(); + } + /* + * Re-program the timer to the new value ... + */ + timerfd_setup(ctx, clockid, flags, &ktmr); + + spin_unlock_irq(&ctx->lock); + fput(file); + } + + return ufd; + +err_tmrcancel: + hrtimer_cancel(&ctx->tmr); + kfree(ctx); + return error; +} + |